The present invention relates to a thermogenic system and more particularly, to means for generating heat in compositions dispensed from container packages.
There is a public need for dispensing means that will dispense warmed or hot compositions for shaving creams, shampoos, cleaning agents, disinfectants, deicers, and the like. Considerable effort has been directed to redox reactions of sulfur-containing organic compounds. Among the more recent thermogenic systems is that described by Moses et al., U.S. Pat. No. 3,341,418, wherein a redox reaction between hydrogen peroxide and thiourea or various thiobarbituric acid derivatives is disclosed. A disadvantage of this process, however is that for every mole of thiourea reacted, one mole of sulfuric acid is formed, necessitating the presence of excess alkali to prevent the destruction of soap in a soap-containing composition.
Another redox heating system is found in Antonelli et al., U.S. Pat. No. 3,632,516, which employs as a reductant, potassium thiosulfate and potassium sulfite with a sodium tungstate catalyst. While oxidation of thiosulfate ion provides a greater heat yield than does the oxidation of thiourea, the problem with the system is the fact that for every mole of thiosulfate oxidized, two moles of sulfate ion are generated requiring again the presence of excess base to prevent the pH from dropping so as to inhibit the formation of a soap. The thiosulfate and sulfite salts tend to cause gelling of soap compositions and are also highly corrosive to metal dispensing containers and to the valve means commonly utilized with such.
Another redox heating system is found in Margolis, U.S. Pat. No. 3,804,771, which employs as a reductant, xanthates, dithiocarbamates, and combinations of formaldehyde and molecular entities incorporating a ##STR2## grouping using hydrogen peroxide as the oxidant. The problem with this system is that again sulfate ion is a reaction product thus necessitating the use of excess alkali to prevent soap degradation. Free formaldehyde is present in the system and may be liberated. Since formaldehyde is a severe skin irritant it is necessary to add a bisulfite salt to the system when it is to be used in personal-care products. The liberation of free formaldehyde is temperature dependent. There is, therefore, an inherent defect in the system: when more heat is generated by the mixing, more free formaldehyde is liberated, thus requiring more bisulfite salt.